Method of operating cathode ray tubes



DCC. 10, 1940. H BHRlNG I 2,224,587

METHOD OF OPERATING CATHODE RAY TUBES Filed July 16, 1937 Paetec D...1o, 194g. g l 2,224,587"

" UNIT-'ED STTES OFFICE r Herlrlrtr zhring, Berlin-Zehlendorf, Germany;

assigner to the firm of Fernseh Aktien-Gesellschaft, Zehlendorf, nearBerlin, Germany Application July 16, 1937, serial No. 154,093 In GermanyJuly 13, 1336 solaims. (o1. 25o-127) This invention relates to anarrangement for occur in oscillographs whereby incorrect curvesoperating cathode ray tubes in which the deare obtained. l` ecting fieldand a magnetic focusing field per- According to the invention all thesedisad-4 r l meate each other. Such tubes are used, for invantages areeliminated by such an arrangement 2 A' 5 stance, as picture analyzersfor television purof the circuit that variations of the deflecting andposes. Y l focusing fields'. caused by variations' of voltages If amagnetic focusing field for electron opare of the same phase and equalin percentage tical reproduction of,y for instance, a photo- Thesimplest way to realizev this idea consists in cathode in aFarnsworth'mage Dissector, persupplying all fields from 'one commonvoltage meates the deflecting fields, a rotation of v'the source, as,for instance,l a common power pack. direction occurs which depends uponthe inten- It hasbeen found that a perfect compensation sity of thefocusing field. This rotation which of Vall variations 'andinterferences can be olo-v occurs in electrostatic as well asmagneticdeflectained in this manner. The compensation is tionis causedby the fact that the electrons are based upon thefact that the angleofdefiection l5 always influenced by the focusing field if they increaseswith increasing intensity of the de- 15l y have a component of -velocitytransverse to the fleeting field, and that it decreases with increasaxisof the tube. Such a component-however, ing intensity of the focusingfield. If the rotais generated in'deection and thus has an addition ofthe picture is 90 degrees, both effects comtional secondary deflectionas a-consequencc. pensate each other. Forelectrostatic deflection.

'20 The rotation of the deflection direction vcauses perfectcompensationisialso obtained lfor peri- .a rotation of the entire imagewhich approaches odical intermediate values; f

a limit of 90 degrees with increasing intensity This invention has theadvantage that `only of the focusing field, one. power pack with littlefiltering is required, When using magnetic deflection, the influencewhereas so far each one of the power packs had y of the focusing fieldupon the direction of the to be extremely carefully filtered.

deflection furthermore causes av distortion of the Different circuitsmay be used for the realizaimage because the secondary deection doestion of the invention. The choice is partly de-Y not occur linearly. Thedistortion is made nopendent on whether the amplitude of the Kippticeable bythe fact that the coordinates of the oscillations dependsupon the voltage applied to scanning field are no longer straight. thecorresponding Kipp circuit or on the current. 30

Only if the intensity of the focusing field is of In the first case theKipp circuit and the focusing such value that the rotation of the imageis apcoil are connected in parallel, whereas in the proximately 90degrees, does this distortion dissecond case a parallel as well asseries connecappear. Thus, this is a requirement for a good tion ispossible. In the case of parallel connecv image, because the intensityof the focusing field tion it is advisable to make the time constants of35 is also, on the other hand, determined by the all branches equal.

dimensions of the tubefand by the accelerating The variations of thevfocusing field will natvoltage for the photoelectrons, these -valuesmust urally also influence the sharpness of the image. also be adjustedto meet the above requirement. However, it has been found that thisinuence is 4c Such arrangements have a certain disadvanslight and doesnot disturb the reproduced image 40 tage, in fact, the sensitivitydepends upon the in any mannerintensity of the focusing field; thus, ifthe cur- The object of the invention may be more clearrent in thefocusing coil varies, the angle of -de- 1y understood from the drawing,of which Figs-` flection also varies so that the image becomes 1 to 3show several embodiments.

distorted.v Non-linear variations of the deflect- In Fig. 1 a power pack2 is connected tojthe 45 ing fields also cause a distortion when thefocuspower supply I. Direct current is taken from ing field' remainsconstant. If variations exist the points 4 and 5 of the power pack. AFarnsthey are harmonics or`sub-harmonics of the worth image dissector,indicated at 9, conscanning frequencies and standing distortion of tainsa photocathode l2 and an anode I3. A

the image occurs. Other variations cause a focusing coil 6 covers theentire length of the l50` momentary flicker. In television transmissiontube and secures electron optical reproduction.. these variations may,for instance, cause the Deflecting coils I0 and Il are provided throughscanning lines to be sinusoidal instead of straight, which saw-toothcurrents flow which are taken which considerably impairs the qualityv ofthe from the Kipp circuits 1 and 8 and which proimage. Correspondinginterference may also duce deecting fields perpendicular tov each 55other. According to the invention the focusing coil 6 as well as theKipp circuits 1 and 8 are all connected to the .output of the same powerpack 2.

Fig. 2 shows a similar circuit. The branches indicated by I and II eachcontain a Kipp circuit. The insuiciently filtered direct-current voltageis applied to the circuit I at the points I5 and I6. The Kipp condenserI8 is slowly charged through a resistor I I so that only a very smallcurrent flows. Block I9 schematically indicates an arrangement whichconsists of a discharge device for the condenser I8 and of an amplifier,the .output of which is connected with the picture frequency deflectingcoil 2E). The arrangement IS corresponds to a very high resistanceduring the charge period, which is long compared with the dischargeperiod and can thus be omitted for this time in the consideration. Thetime constant of this branch is thus equal to the product CR of thecondenser I8 and the resistor I'I. The branch indicated by II representsan equivalent circuit for the line scanning arrangement in which theamplitude may be proportional to the current through the branch. Thebranch indicated by III is an equivalent circuit for the focusing coil.In both cases, the ohmic resistance of the branch is indicated by 22 and23, respectively, and the inductance by ZI and 24, respectively. Inorder to accomplish the compensation of variations or interferencescompletely and especially independently of the frequency, it isadvisable to make the time constants of the three branches equal; thatmeans that L2 La lfl whereby L2, R2, and so forth, indicate theinductance and resistance, respectively, of the corresponding branchesII and III.

Fig. 3 shows a third embodiment in which the Kipp circuits I and II,which are indicated by equivalent circuits, are connected in paralleland then in series with the focusing coil circuit III, which is alsoindicated by an vequivalent circuit. In this case the operation of bothKipp circuits is dependent on the passing current. A similar arrangementis also possible in which, however, one of the two Kipp circuitsoperates according to the applied Voltage.

In al1 cases the deflection can be produced by electrostatic as well aselectromagnetic means. The invention is, of course, applicable also totelevision receiver tubes and oscillograph tubes.

Having thus described my invention, I claim:

1. In combination with a cathode ray tube, an electromagnetic focusingcircuit, a deflecting circuit operable to influence an electron indirections normal to each other, and a common power supply for saidfocusing and deflecting circuits, said circuits having approximatelyequal time constants.

2. Apparatus substantially as set forth in claim l, wherein saidfocussing circuit and said deiecting circuit are connected in parallel.

3. Apparatus substantially as set forth in claim 1, wherein saidfocusing circuit and said deecting circuit are connected in parallel.

4. Apparatus substantially as described in claim 1 having a seriesconnection between said focusing circuit, said deecting circuit and saidcommon power supply.

5. In combination with a cathode ray tube, a cathode ray beam focusingcircuit and a pair of deiecting circuits, all operable to influence anelectron in directions normal to each other, said focusing circuit andsaid deecting circuits having time constants approximately equal to eachother and being energized from a single power supply source.

HERBERT BHRING.

